ToolWindowContainer - Autohide Tabs Margin question

I needed 4 pix Margin all around to be used for a dropshadow and since I have access to source code, I have modified the Style for one Control by modifying what you have as

<Style x:Key="{x:Type docking:ToolWindowContainer}" TargetType="{x:Type docking:ToolWindowContainer}"
BasedOn="{StaticResource RaftableDockingWindowContainerStyleBase}">

The have sucessfully set the template to exactly what I want. Everything works fine, EXCEPT when the Container is set to AutoHide the Tabs that are showing docked to the outer border are not placed correctly. I need them to be shifted 4 pixels. So in a bottom docked container, the first tab should have a margin of 4 on the right side, and if docked to right, it should have a Margin of 4 from the top.

I just can not find the Template for the container that holds these tabs to apply the Margin. Could you tell me where I need to look?